The number = int_number assignment will make the number point to
the stack and as the int_number goes out of scope at the end of
the if statement other code could re-use this stack for other memory.
Fixes: Coverity CID 1042325
Prepend the international number with a '+' and then do the normal
re-writing on it. There are a couple of ways to handle this:
\+([0-9]), \+[0-9][0-9]([0-9]), \+49([0-9])
Add a test case for the international re-write based on an already
internationalized number.
Holger Hans Peter Freyther